1. Field of the Invention
The present invention relates to a crawler which has an endless path of movement and which is used for a vehicle such as a machine used for construction, a machine used for civil engineering or the like. In particular, the present invention relates to a rubber pad of a crawler block.
2. Description of the Related Art
When machines for construction or machines for civil engineering work travel on paved roads, the paved surface may be damaged. As a result, crawler blocks having rubber pads on the outer surfaces thereof have come into use in place of steel crawler blocks.
FIG. 36 is a side view of a conventional crawler using crawler blocks having rubber pads. FIG. 37 is a side view of the crawler trained around a sprocket or an idler.
In the drawings, 1.sub.0 is a link, 2.sub.0 is a crawler block, and 3.sub.0 is a rubber pad vulcanized and adhered to the outer surface of the crawler block 2.sub.0. The links 1.sub.0 and the crawler block 2.sub.0 are fixed by bolts 4.sub.0 and nuts 5.sub.0. Adjacent links 1.sub.0, 1.sub.0 are axially supported by pins 6.sub.0. The crawler is trained around unillustrated track rollers or sprockets or around idlers 7.sub.0 which contact the upper surfaces of the links 1.sub.0 so that the crawler rotates and travels.
Further, when the crawler is trained around a sprocket or the idler 7.sub.0, as illustrated in FIG. 36, the line connecting the pins 6.sub.0, 6.sub.0 of the crawler becomes a neutral line. The crawler rotates with the portions thereof at the inner side of this line narrowing, while the portions thereof at the outer peripheral side of the line widen.
When the crawler is trained around the idler 7.sub.0 or the like, the spaces (W.sub.0) between outer peripheral sides of adjacent crawler blocks 2.sub.0, 2.sub.0 become very large. Therefore, small stones, pieces of ore or the like may become caught in the spaces such that damage to the crawler blocks 2.sub.0 and the rubber pads 3.sub.0 is unavoidable.
Further, crawler rubber shoes in which rubber is vulcanized and adhered to the ground-contacting surface thereof have by preference come into use. FIG. 38 is a ground-contacting surface side plan view illustrating an example of a crawler rubber shoe. FIG. 39 is a side view thereof, and FIG. 40 is a cross sectional view taken along line N--N of FIG. 38.
In the conventional crawler rubber shoe, a metal crawler block 54 is attached by bolts 52 and nuts 53 to connection links 51 which form the crawler. Usually a grouser 55 is formed at the ground-contacting surface side of the metal crawler block 54, i.e., at the outer surface side of the crawler block 54. A rubber pad 56 is vulcanized and adhered so that the grouser 55 is covered.
In the conventional crawler block rubber shoe described above, the rubber pad 56 is vulcanized and adhered to the outer side surface of the metal crawler block 54, and the top surface of the rubber pad 56 is a substantially flat surface.
Depending on the case, the rubber pad 56 may be formed such that, as illustrated in FIG. 41, the center of the top surface thereof is flat, whereas the end portions thereof are formed to have smaller thicknesses.
As a result, when a crawler using this crawler block rubber shoe is used as the traveling device of a machine, peeling of the rubber pad 56 from the metal crawler block 54 occurs easily. Further, the surface pressure on the central portion of the rubber pad 56, which supports the weight of the machine body, becomes much larger than the surface pressure on the end portions. As a result, defects in the rubber concentrate at the central portion where the surface pressure is high.
Moreover, because the grouser 55 is formed at the outer surface side of the crawler block 54 in the longitudinal direction thereof, the thickness of the rubber with respect to the ground-contacting surface of the rubber pad 56 varies. As a result, the compressive strain on the rubber pad 56 varies at the respective portions thereof. The durability of the rubber therefore markedly deteriorates.
When the crawler travels over small stones or the like, the crawler bends toward the inner side, i.e., so-called "reverse bending" occurs at the ground-contacting regions of the crawler. In this case, the end portions of adjacent crawler blocks contact each other so that the reverse bending is stopped. However, usually, there is a large space between the crawler blocks, and even if reverse bending occurs, it is difficult for the end portions to contact each other. Accordingly, it is difficult to prevent reverse bending.
The conventional crawler rubber pad covers the outer surface side of the crawler block and is vulcanized and adhered thereto. During manufacturing, the crawler block is set in a mold, and the remaining space in the mold is filled with rubber. The rubber which has been made fluid moves easily around not only the ground-contacting surface of the crawler block, but also to the inner side thereof. Track links are to be fixed to this crawler block, but because the inner surface of the crawler block and the inner surface of the rubber pad are in the same plane, the protruding of rubber at the inner surface side of the crawler block is quite incommodious, and the entire protruding rubber portion must be removed when the track links are to be attached.
Namely, the protruding rubber which has circled around to the inner side of the crawler block is removed by a knife or by buff finishing. Such processes not only require labor, but also, the main rubber pad body is easily damaged in such processes. Accordingly, there is a need for improvement.